/Engine/Source/Developer/LauncherServices/Public/ILauncherDeviceGroup.h
The first parameter is the device group that invoked the delegate. The second parameter is the identifier of the device that was removed.
typedef TMulticastDelegate_TwoParams< void, const [ILauncherDeviceGroupRef](API\Developer\LauncherServices\ILauncherDeviceGroupRef) &, const [FString](API\Runtime\Core\Containers\FString) & > FOnLauncherDeviceGroupDeviceRemoved